Heat storage device

ABSTRACT

A heat storage device for transferring heat indirectly between a fluid and a heat storing medium, and for storing transferred heat, includes a container that surrounds an interior of the container, the heat storing medium being located in this interior. A plurality of vertical tubes are arranged in the interior of the container, each of these tubes being fluidically connected to a vertical header tube by means of a lower end section. Each of the tubes has a plurality of heat transfer fins that contact the heat storing medium.

The invention relates to a heat storage device according to claim 1.

Such heat storage devices serve for the indirect heat transfer between a fluid and a heat storage medium, and also for storing the heat transferred from the fluid to the heat storage medium.

The heat storage medium can be, in particular, a phase change material (PCM), using which the heat of a fluid, which can be any desired process medium or a process stream, can be stored or liberated at a virtually constant temperature using the latent heat (e.g. in the liquid-solid phase transition). On account of the jump of the specific volume between the solid and liquid phase of the heat storage medium, the phase transition must take place continuously with respect to space, in order to avoid local pressure differences. These pressure differences would otherwise lead to a mechanical overloading of the heat-transfer system between the fluid and the heat storage medium or phase change material.

It is known to date (cf. e.g. KR20000033239) that tubes through which the fluid or process medium flows and which are provided with external heat transfer fins are arranged horizontally in the container accommodating the heat storage medium. In this case, however, a uniform melting or freezing of the heat storage medium is not ensured.

In addition, concepts are known (cf. e.g. CN102777874), in which the tubes are conducted vertically with their external heat transfer fins between two tube sheets. The lower tube sheet in this case must, however, withstand the full weight of the heat storage medium. In the case of large volumes of heat storage medium, therefore, tube sheets having a diameter of several meters would be necessary.

Proceeding therefrom, the present invention addresses the problem of improving a heat storage device of the type mentioned at the outset to the extent that the abovementioned disadvantages are at least in part reduced.

This problem is solved by a heat storage device having the features of claim 1. Advantageous embodiments of the invention are specified in the corresponding subclaims and/or are described hereinafter,

According to claim 1, it is provided according to the invention that, in the interior space of the container, a multiplicity of tubes is arranged each of which extends along a longitudinal axis, wherein the tubes and/or the longitudinal axes—based on a heat storage device arranged according to specifications—proceed along the vertical, wherein each of the tubes, at a lower end section of the respective tube, is flow-connected to a (in particular single) likewise vertically proceeding header tube (i.e. the header tube extends along a longitudinal axis which proceeds along the vertical, relative to a heat storage device arranged according to specifications). The flow connections can be formed, e.g., in each case by a tube conduit section and/or flow path proceeding along the horizontal, which section and/or path connect the respective tube to a lower section of the header tube or via a header (see below). In addition, the tubes according to the invention have a multiplicity of heat transfer fins that contact the heat storage medium in order to ensure heat transfer that is as good as possible between the fluid and the heat storage medium.

The heat storage device is preferably constructed in order to conduct the fluid (e.g. steam) from top to bottom in the respective tube during storage of heat, in such a manner that heat is transferable from the fluid flowing in the respective tube to the heat storage medium, wherein the heat storage device further preferably is constructed in order to conduct the fluid from bottom back to top in the header tube, wherein the fluid is withdrawable in particular via the header tube. For delivery of heat, the heat storage device is preferably constructed in order to conduct the fluid (e.g. water) via the header tube from top to bottom and via the tubes from bottom back to top, in such a manner that heat is transferable from the heat storage medium to the fluid.

Preferably, the heat transfer fins in this case can each project in a radial direction of the respective tube away from a shell of the respective tube, or in another manner be fixed on the respective tube. The heat transfer fins can also project in a radial direction from an additional carrier which is fixed on a shell of the respective tube. The carrier can itself be designed so as to be tubular or dish-shaped. In particular, the respective carrier can have two dishes which are opposite one another and surround the respective shell on which they are fixed. Then, the heat transfer fins project e.g. in a radial direction, from the carrier or from the dishes. The heat transfer fins can be molded in a one-piece manner onto the carrier or the dishes, or be connected thereto in another way (e.g. weld connections)

On account of the increased effective surface area of the tubes due to the fins, improved heat transfer occurs between the fluid and the heat storage medium.

With the heat storage device according to the invention, firstly heat of a fluid and/or a process medium can be transferred thereby to the heat storage medium and stored therein and/or, secondly, heat stored in the heat storage medium can be transferred to a fluid and/or process medium.

Owing to the vertically arranged tubes, a spatially homogeneous melting and/or freezing of the heat storage medium around the tubes is possible, wherein, in particular, additionally owing to the conducting of the fluid through the tubes (with recirculation and/or feeding through a header tube), a lower tube sheet is dispensable, and so the weight of the heat storage medium need not be deflected via a lower tube sheet, but, e.g. via a correspondingly designed container bottom. Preferably, therefore, the tubes and also optionally the header tube and the flow connection between the tubes and the header tube are held from the top, in particular via a distributor or a tube sheet and/or other internals.

As already mentioned at the outset, the heat storage medium is preferably a phase change material, that is to say a material, the latent heat of melting, heat of solution or heat of absorption of which is greater than the heat which it can store owing to its specific heat capacity (without the phase conversion). The heat storage device is correspondingly also termed a latent heat storage device. The heat storage medium can be, e.g., a nitrate salt, and/or the heat storage medium can comprise a nitrate salt such as, e.g., NaNO₃ or KNO₃. The heat storage medium can also comprise a mixture of nitrate salts, in particular a mixture of NaNO₃ and KNO₃.

For distribution of the fluid between the tubes, preferably a distributor is provided that is flow connected to the tubes at an upper end of the tubes in such a manner that the fluid is feedable into the respective tube via the distributor.

According to a preferred embodiment of the invention, it is provided that the distributor comprises at least one (in particular annular) tube conduit having respectively a first chamber and a second chamber separate therefrom.

Of course, a plurality of said annular tube conduits can also be provided that then preferably are arranged concentrically with one another in a plane, According to an alternative variant of the heat storage device according to the invention, the distributor can also comprise a tube sheet in which the tubes are respectively anchored by their upper end. The distributor can, in addition, comprise a further tube sheet in which the header tube is anchored.

According to an embodiment with header tube for taking off and optionally feeding the fluid, it is preferably provided that the tubes are each anchored with an upper end in a tube sheet of the distributor, in such a manner that the fluid is feedable (or removable) via the tube sheet into (out of) the respective tube, and flows downwards or upwards, respectively, therein. The header tube in this case is preferably passed through the tube sheet by an upper end section, or a corresponding flow path is conducted through the tube sheet.

In addition, the tube sheet, with a preferably hood-shaped cover of the container, can delimit a chamber of the distributor into which the fluid is introducible via a port or from which the fluid is removable via the port. The fluid introduced into the chamber can then pass into the tubes via the tube sheet or can be removed from the tubes via said chamber.

The header tube is preferably arranged centrally in the container along the vertical, wherein the tubes are preferably arranged further outside radially, and preferably arranged distributed around the header tube.

According to a further embodiment of the invention, it is provided that the flow connection between the tubes and the header tube comprises a header, or is produced via a header, wherein the tubes each open out via a lower end-side opening of the respective tube into the header, and wherein the header tube opens out via a lower end-side opening of the header tube into the header. The header tube, the tubes and the header can be carried by the tube sheet.

According to an embodiment, it is provided in this case that the header has a convex shell that delimits an interior space of the header for collecting the fluid, wherein, in particular, at least one upper region of the shell of the header is constructed so as to be spherical segment-shaped. Preferably, the tubes open out into said upper region of the header, wherein, preferably, the header tube opens out into the header at a highest point of the header or of the shell of the header. Preferably, the shell of the header is designed so as to be cylindrically symmetrical, wherein the cylinder axis coincides with the longitudinal axis of the header tube that opens out into the header from the top.

According to a further preferred embodiment, it is provided that the interior space of the container, for preventing cavities in the event of a solidification of the heat storage medium, comprises a region surrounding the header tube, or a region in which the header tube is arranged, wherein none of the tubes is arranged in the region. Said region extends preferably along the header tube. Via this region (which is also termed feeder), in which none or a reduced heat transfer takes place, on solidification of the heat storage medium, fluid heat storage medium is subsequently delivered, in particular downwards, and also outwards, towards the tubes. The region preferably has a diameter that is at least twice as large as the outer diameter of the header tube. Preferably, the diameter of the region is additionally selected in such a manner that here the heat storage medium becomes solid last. If this is the case, the diameter optionally can also be smaller.

In addition, the header tube can also be constructed without additional insulation. An insulation can then be achieved by the insulating action of the (solidified) heat storage medium and/or salt. The central region then preferably has a correspondingly greater diameter, via which the desired insulation is provided.

To provide the required amount of fluid heat storage medium, the interior space of the container, at the upper end of the tubes, has a region or a partial volume which borders, e.g. on the tube sheet, and in which said amount of fluid heat storage medium is providable. In this region or partial volume of the interior space, the tubes preferably do not have heat transfer fins.

In addition, it can likewise be provided that the tubes each have a lower section via which the respective tube opens out into the header, wherein, likewise, no heat transfer fins are provided on said sections.

In all embodiments of the invention, it can be provided that the container is constructed as an inner container that is arranged in an interior space of an outer container in such a manner that an intermediate space is present between the shell of the inner container and a shell of the outer container.

The intermediate space or parts of the intermediate space can be evacuated and/or be filled with an insulation material (e.g. in the form of a bed).

In addition, the inner container can be suspended via a suspension bracket on the shell of the outer container.

In addition, in all embodiments, on a lower region or base of the shell of the container or inner container, a port can be provided for charging the interior space of the container or inner container with heat storage medium and/or for removing heat storage medium from the interior space of the container or inner container. The port in this case can have a heating device such that the heat storage medium can optionally be transferred into the liquid state of matter.

Further features and advantages of the present invention will be explained in the description of exemplary embodiments with reference to the figures. In the figures:

FIG. 1 shows a schematic sectional view of an embodiment of a heat storage device according to the invention;

FIG. 2 shows a schematic detailed sectional view of an alternative embodiment of the distributor according to FIG. 1

FIG. 3A shows a schematic sectional view of a tube of a heat storage device according to the invention;

FIG. 3B shows a further schematic sectional view of a tube of a heat storage device according to the invention;

FIG. 4 shows a sectional view of a further embodiment of a heat storage device according to the invention.

FIG. 1, in combination with FIG. 3A and FIG. 3B, shows an embodiment of a heat storage device 1 according to the invention that has a container 10 having a shell 11 that delimits an interior space I of the container 10, wherein a heat storage medium P in the form of a phase change material is arranged in the interior space I. In the interior space I of the container 10, in addition, a plurality of tubes 24 are arranged each of which extend along a longitudinal axis, wherein the longitudinal axes proceed parallel to the vertical z, relative to a state arranged according to specifications of the heat storage device 1. The tubes 24 in this case are surrounded by the heat storage medium P and contact it in such a manner that a fluid F conducted in the tubes 24 can come into an indirect heat transfer with the heat storage medium P. The tubes 24 are constructed in accordance with FIG. 3A or FIG. 3B.

Each tube 24 is constructed to conduct said fluid F along the vertical z downwards. At a lower end section 24 a, the tubes 24 are connected via a flow connection each to a central header tube 25, in which the fluid F is conducted back upwards. The flow connections can be formed, e.g., by tube conduit sections 245 proceeding along the horizontal, which tube conduit sections connect the respective tube 24 to a lower section of the header tube 25.

The fluid F is then introduced into the respective tube 24 by means of a distributor 35 preferably at an upper end 24 b of the respective tube 24, then flows downwards along the vertical z or longitudinal axis in the respective tube 24 and then flows via the tube conduit sections 245 into the header tube 25 and then flows therein back up (the distributor 35 can also be constructed as a double tube sheet in the manner of FIG. 2, wherein the tubes 24 are anchored in the first tube sheet 310 and the header tube 25 in the further tube sheet 320). In this case, the fluid F, on its path downwards in the tubes 24, can exchange heat with the heat storage medium P. Thus, for example, the fluid F can melt the heat storage medium P that is situated in the solid state of matter, wherein the heat storage medium P takes up relatively much heat energy (heat of melting). At a later time point, the heat storage medium P can be run down as required, by bringing the heat storage medium P to solidification, wherein the heat storage medium P gives off the amount of heat previously taken up as heat of solidification back to the fluid F conducted in the respective tube 24, which fluid is correspondingly warmed.

In addition, the header tube 25 can have a heat insulation 253. Thus, the header tube 25 can be constructed as a double tube that comprises an inner tube 252 and also an outer tube 251 surrounding the inner tube 252, wherein the heat insulation 253 can be arranged in a ring gap 254 between the inner tube 252 and the outer tube 251 of the header tube (25).

Owing to the circumstance that the respective tube 24 is charged with the fluid F at the upper end 24 b, or the fluid F is taken back off at the upper end of the header tube 25, a tube sheet at the lower end 24 a of the tubes 24 can be dispensed with. The load of the heat storage medium P therefore need not in turn be intercepted by a lower tube sheet, but can be introduced in a correspondingly strengthened substrate, or into a suitably dimensioned container bottom of the container 10.

A typical cross section of a tube 24 according to the invention is shown in FIG. 3A. In this case, the respective tube 24 preferably has a cylindrical shell 210, from which heat transfer fins 211 project in a radial direction, which fins ensure an enlargement of the effective surface area of the shell 210 of the tube 24, in such a manner that the heat transfer between the respective tube 24 and the surrounding heat storage medium P is improved.

FIG. 3B shows a further embodiment of a tube 24 according to the invention, wherein, in contrast to FIG. 3A, here the heat transfer fins 211 are fixed to separate dish-shaped carriers 212, 213 that are fixed in pairs to the shells 210 of the tubes 24. In this case, the carriers 212, 213 that are arranged on a shell 210 can be fixed to one another, in order to achieve an attachment to the respective outer tube 21.

FIG. 2 shows an embodiment of a distributor 35 that is an alternative to FIG. 1, which can be used in a heat storage device 1 according to FIG. 1 instead of the distributor 35. The distributor 35 in this case is constructed as a double tube sheet which has two parallel tube sheets 310, 320, namely a (first) tube sheet 310, in which the header tube 25 is anchored, and also a parallel further (second) tube sheet 320, in which the respective tubes 24 are anchored. Between the two tube sheets 310, 320, a first chamber 301 is then formed, into which the liquid medium F can be introduced, in such a manner that it can pass into the respective tubes 24 through through-flow openings 311 of the first tube sheet 310. In addition, the liquid phase F which is returned in the header tube 25 can be passed through through-flow openings 321 of the further tube sheet 320 into an adjacent second chamber 302, from which the liquid phase F can be taken off and fed to further use.

FIG. 4 shows a sectional view of a further heat storage device 1 according to the invention. The heat storage device 1 comprises a container 10 a in the form of an inner container, the shell 11 a of which surrounds an interior space I of the container 10 a, wherein a heat storage medium P is arranged in the interior space I. The container 10 a is arranged in this case in an interior space that is delimited by a shell 11 b of an outer container 10 b, in such a manner that, between the inner container 10 a and the outer container 10 b, an intermediate space is provided which is preferably evacuated and is filled with a heat insulation 10 c, e.g. in the form of a bed.

The container 10 a is preferably mounted or suspended via a suspension bracket 12 on the shell 11 b of the outer container 10 b. The weight of the two containers 10 a, 10 b is introduced into the substrate via feet 13 of the outer container 10 b.

For charging the interior space I of the container 10 a with heat storage medium P, or for removing heat storage medium P from the interior space I of the container 10 a, a port 600 is provided which preferably has a heating device 601, such that the heat storage medium P can be kept in the liquid state of matter during discharge or inflow.

For the heat transfer with the heat storage medium P, a multiplicity of tubes 24 are provided in the interior space I of the container 10 a, which tubes in each case extend along the vertical z and are surrounded by the heat storage medium P or contact this. The tubes 24 can in turn, as already described above, have heat transfer fins 211 (e.g. according to FIGS. 3A and 3B without inner tubes 22).

The tubes 24 are in addition anchored in a tube sheet 401 of a distributor 400 of the container 10 a, by an upper end 24 b, on which the tubes 24 each have an upper end-side opening 242, in such a manner that the fluid F is feedable into the respective tube 24 or is removable therefrom via the tube sheet 401, and can be conducted therein downwards or upwards. In this case the tube sheet 401 with an upper cover 10 d of the container 10 a delimits a chamber 404 of the distributor 400, into which chamber the fluid F is introducible into the chamber 404 via a port 405 which is arranged on the upper cover 11 d of the outer container 11 b, and also a tube conduit 402 connecting to the port 405 which opens out into the chamber 404. Likewise, the fluid F can be taken off via the tube conduit 402 and the port 405 from the chamber 404. In addition, the fluid F that is introduced into the chamber 404 can pass via the tube sheet 401 into the tubes 24 or can be taken off from the tubes 24 via that chamber 404.

On a lower end section 24 a, the tubes 24 have an end-side lower opening 241, via which the tubes 24 each open out into a header 500. The header 500 has a shell 501 which is constructed to be cylindrically symmetrical to the longitudinal axis of the container 10 a (or the header tube 25, see hereinafter) and delimits an interior space I″ of the header 500, wherein an upper region 502 of the shell 501 or of the header 500 is constructed so as to be a spherical segment shape. The tubes 24 in this case open out via said upper region 502 into the interior space I″ of the header 500.

To remove the fluid F from the header 500 or for introduction of the fluid F into the header 500, in turn, a vertical header tube 25 is provided that runs parallel to the tubes 24, more precisely centrally in the container 10 a along the vertical longitudinal axis of the container 10 a, wherein the tubes 24 are preferably arranged radially further outside and are preferably grouped around the header tube 25. The header tube 25 has a lower end-side opening 250, via which the header tube 25 opens out into a highest point of the header 500. The header tube 25 is passed through the tube sheet 401 with its upper end section 25 a and is flow-connected to a port 406 on the upper cover 11 d of the outer container 11 b, via which port the fluid F is removable from the header tube 25 or via which the fluid F is introducible into the header tube 25. The heat storage device 1 is therefore configured in such a manner that the feeding and removal of the fluid F proceeds from the top.

For loading the heat storage device 1 (i.e. storage of heat), the fluid F, e.g. steam, is fed into the tubes 24 via the distributor 400, i.e. via the port 405, the chamber 404 and the tube sheet 401, flows downwards in the tubes 24, wherein heat is given off to the heat storage medium P, which is liquefied in the course of this. The cooled fluid F (e.g. cooled steam) is taken off again via the header 500 and the header tube 25 and also the port 406 and supplied to the further use thereof. To run down the heat storage device 1 (i.e. discharge of heat), the fluid F (e.g. water) is added into the header tube 25 via the port 406, flows therein downwards into the header 25 and is passed back upwards therefrom via the tubes 24 and is taken off via the distributor 400. In the tubes 24, the fluid F can take up heat from the heat storage medium P, which in this case can be made to solidify.

To avoid cavities in the event of a solidification of the heat storage medium P, a central region 13 of the interior space I of the container 10 a surrounding the header tube 25 is provided in which central region none of the tubes 24 is arranged, in such a manner that substantially no heat transfer takes place there. Via this region B, in the event of solidification of the heat storage medium P, fluid heat storage medium P is subsequently supplied. An amount of fluid heat storage medium P required therefor is provided in a partial volume V of the interior space I of the container 10 a at the upper end 24 b of the tubes 24. In this region or partial volume V of the interior space I, the tubes 24 preferably have no heat transfer fins 211, in order to decrease the heat transfer here. The partial volume V is labeled by the two levels P′ and P″. The solid solidified heat storage medium P has the lower level P′; the liquid heat storage medium P has the higher level P″. In addition, the tubes 24 likewise have no heat transfer fins 211 in each case at the lower end section 24 a, via which the tubes 24 open out into the header 25. These lower end sections 24 a of the tubes 24 can, furthermore, have a bend or a kinked course, in such a manner that the tubes 24 can each open out perpendicularly into the shell 501 of the header 500.

REFERENCE SIGNS

1 Heat storage device or latent heat store 10, 10a Container, in nartieular inner container 10b Outer container 10d, 11d Cover 11, 11a, 11b Shell 12 Suspension bracket 13 Foot 25a Lower end 24b Upper end 251 Outer tube 252 Inner tube 254 Ring gap 24 Tube 24a Lower end section 25 Header tube 25a Upper end section 35, 300, 400 Distributor 31 Annular tube conduit 32 First chamber 33 Second chamber 210, 240 Shell 211 Heat transfer fins 212, 213 Carrier 220, 250, 241 Lower end-side opening 221, 242 Upper end-side opening 222, 253, 10c Heat insulation 245 Tube conduit section or flow connection 301 First chamber 302 Second chamber 310, 401 Tube sheet 311 Through-flow opening 320 Further tube sheet 321 Through-flow opening 402 Tube conduit 404 Chamber 405, 406, 600 Port 500 Header 501 Shell 502 Upper region B Free region I, I′, I″ Interior space F Fluid P Heat storage medium P′, P″ Level V Volume Z Vertical 

1. A heat storage device for indirect heat transfer between a fluid and a heat storage medium, and also for storing transferred heat, having: a container that surrounds an interior space of the container, wherein the heat storage medium is arranged in the interior space, characterized in that a multiplicity of vertical tubes is arranged in the interior space of the container, wherein the tubes are each surrounded by the heat storage medium, wherein the tubes are each flow-connected via a lower end section to a vertical header tube, wherein the tubes each have a multiplicity of heat transfer fins, wherein the heat transfer fins contact the heat storage medium.
 2. The heat storage device as claimed in claim 1, characterized in that the heat storage medium is a phase change material.
 3. The heat storage device as claimed in claim 1, characterized in that the fluid can be conducted into the tubes in two flow directions.
 4. The heat storage device as claimed in claim 1, characterized in that the tubes are each flow-connected at an upper end to a distributor in such a manner that the fluid is feedable into the respective tube via the distributor.
 5. The heat storage device as claimed in claim 4, characterized in that the distributor comprises a tube sheet in which the tubes are anchored.
 6. The heat storage device as claimed in claim 4, characterized in that the distributor comprises a further tube sheet in which the header tube is anchored.
 7. The heat storage device as claimed in claim 1, characterized in that the header tube is arranged centrally in the container, wherein the tubes are arranged distributed around the header tube.
 8. The heat storage device as claimed in claim 1, characterized in that the header tube has a heat insulation, wherein, in particular, the header tube is constructed as a double tube that comprises an inner tube and also an outer tube surrounding the inner tube, wherein the heat insulation is arranged in a ring gap between the inner tube and the outer tube of the header tube.
 9. The heat storage device as claimed in claim 1, characterized in that the flow connection between the tubes and the header tube comprises a header, wherein the tubes each open out via a lower opening of the respective tube into the header, and wherein the header tube opens out via a lower opening of the header tube into the header.
 10. The heat storage device as claimed in claim 9, characterized in that the header has a convex shell that delimits an interior space of the header, wherein, in particular, at least one upper region of the shell of the header is constructed so as to be spherical segment-shaped.
 11. The heat storage device as claimed in claim 1, characterized in that the interior space, for preventing cavities in the event of a solidification of the heat storage medium of the container, comprises a region surrounding the header tube, in which region none of the tubes is arranged. 